1. Field of the Invention
The present invention relates to a method for the production of hydroxylated nickel compounds, and, more particularly, to a method for the production of highly pure nickel hydroxide from a solution of dissociated nickel salts. It also relates to the electrolytic preparation of a basic nickel salt having a special structure, its purification, and the preparation of highly pure nickel hydroxide therefrom.
2. Description of the Prior Art
The preparation of oxidized nickel compounds, e.g., the hydroxides, the basic carbonates, the carbonates, and the black and green oxides, is particularly difficult and complex. The complexities involved in the production of the black and green oxides are shown in "Production of Nickel Oxide from Ammoniacal Process Streams", Canadian Mining and Metallurgical (Journal), March 1970, pages 352 to 362. To further complicate matters, the composition of the basic carbonates of nickel, especially its nickel content, disadvantageously varies over time.
The nickel hydroxides, given their proper meaning, do not possess these disadvantages. It is, however, very difficult to prepare them in a pure state. In addition, when prepared from their salts, it is generally impossible to recover the anion with which the nickel ion is associated.
Pure nickel hydroxide is difficult to prepare due, in part, to its gelatinous nature, its poor filterability, and, in part, its tendency to absorb ions present in the medium, i.e., the anions associated with the nickel and the cations associated with the hydroxyls. These problems exist regardless of the method used to introduce the hydroxyl ions--whether it is the addition of a base or the electrolytic decomposition of water; the problems are particularly acute in the electrolytic technique, the subject of Societe Le Nickel's French Pat. No. 1,441,749, which relates to a method for producing nickel hydrate by electrolysis, which employs anodes of nickel mattes in an aqueous electrolyte of a chloride or sulfate of an alkaline of alkaline-earth metal with a low current density, a pH of 8 to 10, and a purifying treatment. This prior art method disadvantageously involves a low electrolytic cell productivity, in addition to the difficulties involved in filtering the hydroxide precipitate, which necessitates thorough washing.
Therefore, one of the objects of the present invention is the provision of basic nickel salt that can be easily filtered and readily converted to a highly pure nickel hydroxide.
Another object of the present invention is the provision of a method for producing this basic salt.
Yet another object of the present invention is the provision of a procedure for converting this basic salt to a highly pure nickel hydroxide.
A further object of the present invention is the provision of a method for producing highly pure nickel hydroxide from a dissociated nickel salt combined with the recovery of the associated anion, and in particular when the anion is chloride.
Still further objects and advantages of the present invention will become apparent upon reading the undergoing specification and claims.